This invention relates to lifting assemblies, and more particularly to portable raising and lowering devices often referred to as hoists, winches or lifts. More particularly, although not exclusively, the invention relates to such devices intended for increasing lifting and lowering capacity of manual hoists commonly known as chain falls. The invention also relates to equipment used as parts of, or for operation of, such devices.
Typical chain hoists are manually operated. Such devices are used for raising and lowering loads in small warehouses, garages, small shops and other situations, where overhead cranes are not practical or prohibitively expensive. The chain of a manual chain hoist is wrapped around a drum, or load-chain, and is raised by a pulley with a special profile to engage the chain. Chain hoists may have a lever to actuate the hoist or have a loop of operating chain that the user pulls through the block (known traditionally as a chain fall) which then activates the block to take up the main lifting chain.
Raising and lowering of loads using manual chain hoists takes a considerable time. As the user pulls on one side of an endless loop chain the chain is engaged in a compound pulley with two different radii. The teeth of the pulley engage the endless chain, allowing the exerted force to be multiplied. However, even with the chain hoists using the chain fall the job of lifting and lowering a heavy load is arduous and slow.
There exist motorized lifting devices that use electrical, hydraulic or pneumatic power. Such devices can be found in large manufacturing facilities, distribution centers and the like. There is a need to provide an inexpensive lifting device that can retrofit an existing pulley-mounted chain hoist into a motorized lifting device to reduce manual labor involved in lifting and lowering of heavy loads.